The present disclosure relates to semiconductor memory, memory devices incorporating such memory, and electronic devices incorporating such memory. Generally, the memory devices of the present disclosure comprise a semiconducting layer. The semiconducting layer is formed from an organic semiconductor (i.e. a compound or a polymer) and a photo-responsive material (i.e. a compound or a polymer). The resulting memory device has a good retention, access time, write/erase speed, and power consumption.
Electronic memory devices are generally implemented as a semiconductor-based integrated circuit. Semiconductor memory has the property of random access, which means that it takes the same amount of time to access any memory location, so data can be efficiently accessed in any random order. Semiconductor memory also has much faster access times than other types of data storage; a byte of data can usually be written to or read from semiconductor memory within a few nanoseconds.
In a semiconductor memory device, data is stored in a circuit called a memory cell that consists of one to several transistors. Each transistor is generally composed of, on a substrate, an electrically conductive gate electrode, source and drain electrodes, an electrically insulating gate dielectric layer which separate the gate electrode from the source and drain electrodes, and a semiconducting layer which is in contact with the gate dielectric layer and bridges the source and drain electrodes.
Memory may be classified as volatile or nonvolatile. Volatile memory, such as DRAM, loses its stored data when the power to the memory chip is turned off. Nonvolatile memory (e.g. flash memory) preserves the data stored in it during periods Volatile DRAM has a short retention cycle; the industry standard requires refreshing every 64 milliseconds, i.e. more than 10 times per second. This results in high power and overhead requirements. Flash memory can have a cycle life of up to 10,000 write/erase cycles, has a relatively slower write/erase speed compared to DRAM, and requires high voltages (greater than 15 V) to operate, but has good retention of 10 years or more of the data written therein. As the density of flash memory increases, reliability problems arise due to crosstalk and the limited life cycle.
Some drawbacks of silicon-based electronics include their rigidity and the need of high temperatures for fabrication. These properties impede the use of such devices on flexible substrates such as plastics, cloths, and paper.
It would be desirable to develop a memory device that uses nonvolatile memory with a faster write/erase speed and longer cycle life than flash memory, and with a longer retention cycle than DRAM. Such devices would have several applications in conventional microelectronics. In addition, providing such devices in flexible and printable formats would be useful in low-cost non-silicon electronic devices as well. Longer data retention time should also reduce power consumption.